Increase in surface quality

Abstract

A method for providing control data for a generative layer construction device includes accessing layer data records that have data models of buildup material layers to be selectively solidified, where a base surface region of an object cross section exists in at least one layer data record, where in at least one of p layers below the base surface region, no solidification of buildup material is specified. The method further includes changing the layer data record such that a temporal sequence for scanning the associated object cross section with energy radiation is specified such that at least one portion of the base surface region is scanned before all other parts of the object cross section; and a third step, where the changed layer data record is provided for the generation of a control data record for the device.

The invention claimed is: 
     
       1. A computer-based method of providing control data for a layer-wise additive manufacturing apparatus for manufacturing an object, wherein in the layer-wise additive manufacturing apparatus the object is manufactured by a layer-wise application of a building material onto a support or a previously applied layer of the building material and by a solidification of the building material by a supply of radiation to positions in a layer that correspond to a horizontal cross-section of the object in the layer in that these positions are scanned with energetic radiation by an energy input unit such that the energy input unit directs at least one energy beam to predetermined positions of a layer of the building material so that a solidification of the building material is effected by the energy beam, wherein the method of providing control data comprises:
 a first step of accessing a plurality of layer datasets comprising data models of a plurality of building material layers to be selectively solidified during the manufacture and lying immediately one over the other, wherein each layer dataset comprises a data model in which positions corresponding to an object cross-section are marked, a solidification of the building material in the respective layer occurring at the positions, and wherein in at least one layer dataset a bottom surface region of an object cross-section exists in the corresponding data model, wherein the bottom surface region is defined such that in at least one of p layers below the bottom surface region no solidification of building material is specified, wherein p is a predefined natural number, and/or a top surface region of an object cross-section exists wherein the top surface region is defined such that in at least one of q layers above the top surface region no solidification of building material is specified, wherein q is a predefined natural number; 
 a second step of modifying the at least one layer dataset such that a temporal sequence for the scanning of the respective object cross-section with energetic radiation is specified such that at least one portion of the bottom surface region, or at least one portion of the top surface region, is scanned and solidified before all other positions to be solidified of the object cross-section in the respective object cross-section, where the at least one portion of the bottom surface region and the at least one portion of the top surface region are less than the respective cross-section; and 
 a third step of providing the at least one layer dataset that has been modified in the second step for the generation of a control dataset for the layer-wise additive manufacturing apparatus. 
 
     
     
       2. A method for generating a control dataset for controlling a layer-wise additive manufacturing method for manufacturing an object, wherein the object is manufactured by a layer-wise application of a building material onto a support or a previously applied layer of the building material and by a solidification of the building material by a supply of radiation to positions in a layer that correspond to the cross-section of the object in the layer in that the positions are scanned with energetic radiation by an energy input unit that directs at least one energy beam to predetermined positions of the layer of the building material so that the solidification of the building material is effected by the energy beam, the method comprising:
 a first step of accessing a plurality of layer datasets comprising data models of a plurality of layers of the building material to be selectively solidified during the manufacture and wherein the layers of the building material lie immediately one over the other, wherein each layer dataset comprises a data model in which positions corresponding to an object cross-section are marked, wherein a solidification of the building material in the respective layer occurs at the positions, and wherein in at least one layer dataset a bottom surface region of an object cross-section exists in the corresponding data model in which the bottom surface region is defined such that in at least one of p layers below the bottom surface region no solidification of building material is specified, wherein p is a predefined natural number, and/or a top surface region of an object cross-section exists in which the top surface region is defined such that in at least one of q layers above the top surface region no solidification of building material is specified, wherein q is a predefined natural number; 
 a second step of modifying the at least one layer dataset such that a temporal sequence for the scanning of the respective object cross-section with energetic radiation is specified such that at least one portion of the bottom surface region or at least one portion of the top surface region is scanned and solidified before all other positions to be solidified of the object cross-section in the respective object cross-section, where said at least one portion of the bottom surface region and the at least one portion of the top surface region are less than the respective cross-section; and 
 a third step of providing the at least one layer dataset that has been modified in the second step for the generation of the control dataset for the layer-wise additive manufacturing apparatus. 
 
     
     
       3. The layer-wise additive manufacturing method of  claim 2 , further comprising:
 assigning exposure areas to the at least one portion of the bottom surface region, and/or to the at least one portion of the top surface region; and 
 specifying a scanning of the building material with at least one energy beam in scanlines that are in parallel to each other in each exposure area. 
 
     
     
       4. The layer-wise additive manufacturing method of  claim 3 , wherein in case a dimension of a portion across which an energy beam is to be moved is so small and/or a velocity of movement of an energy beam across the building material is so large that in the scanning along a first scanline a predetermined minimum length of time is underrun, a waiting time after the scanning of the first scanline is specified before the energy beam is moved along a second scanline and/or a radiation energy input per unit area along the first scanline and/or the second scanline is lowered. 
     
     
       5. The layer-wise additive manufacturing method of  claim 4 , wherein a value smaller than 25 is specified for p and/or q. 
     
     
       6. The method for generating a control dataset of  claim 2 , further comprising:
 directing a gas flow over the respective position of incidence of an energy beam; and 
 controlling the process of the layer-wise additive manufacturing method by the control dataset by specifying that the object cross-section has positions in the layer outside of the bottom surface region that are located further upstream than positions in the at least one portion of the bottom surface region and/or that the object cross-section has positions in the layer outside of the top surface region that are located further upstream than positions in the at least one portion of the top surface region. 
 
     
     
       7. The method for generating a control dataset of  claim 6 , further comprising:
 controlling the process of the layer-wise additive manufacturing method by the control dataset by specifying that the object cross-section has positions in the layer outside of the bottom surface region that are located further upstream within an angular range around the direction the gas flow is coming from than positions in the at least one portion of the bottom surface region and/or that the object cross-section has positions in the layer outside of the top surface region that are located further upstream within an angular range around the direction the gas flow is coming from than positions in the at least one portion of the top surface region. 
 
     
     
       8. The method for generating a control dataset of  claim 7 , further comprising specifying as the angular range a range between −22.5° and +22.5° around the direction the gas flow is coming from. 
     
     
       9. The method for generating a control dataset of  claim 2 , wherein the energy input unit is controlled such that the scanning direction, in which the energy beam is moved over the building material at a solidification position and the direction of the gas flow at the solidification position, are at an angle that is larger than or equal to 22.5° and/or smaller than or equal to 337.5°. 
     
     
       10. The method for generating a control dataset of  claim 2 , further comprising:
 controlling the energy input unit such that the scanning directions of two neighbouring scanlines are opposed to each other in at least one exposure region, 
 wherein an advance direction in which the scanlines in the exposure region are subsequently scanned with the at least one energy beam and the direction of the gas flow averaged over all positions of the at least one exposure region are at an angle that is larger than or equal to 112.5° and/or smaller than or equal to 247.5°. 
 
     
     
       11. The method for generating a control dataset of  claim 2 , further comprising:
 controlling the energy input unit such that the scanning directions of all scanlines in an exposure region are the same, 
 wherein an advance direction in which the scanlines in the exposure region are subsequently scanned with the at least one energy beam and the direction of the gas flow averaged over all positions of the at least one exposure region are at an angle that is larger than or equal to 22.5° and/or smaller than or equal to 337.5°, and 
 the scanning directions and the direction of the gas flow averaged over all positions of the at least one exposure region are at an angle that is larger than or equal to 90°. 
 
     
     
       12. The layer-wise additive manufacturing method of  claim 2  further comprising:
 providing a data access unit configured to access a plurality of layer datasets comprising data models of a plurality of building material layers to be selectively solidified during the manufacture and lying immediately one over the other, wherein each layer dataset comprises a data model in which positions corresponding to an object cross-section are marked, wherein a solidification of the building material in the respective layer occurs at the positions, and wherein in at least one layer dataset a bottom surface region of an object cross-section exists in the corresponding data model, wherein the bottom surface region is defined such that in at least one of p layers below the bottom surface region no solidification of building material is specified, wherein p is a predefined natural number, and/or a top surface region of an object cross-section exists, wherein the top surface region is defined such that in at least one of q layers above the top surface region no solidification of building material is specified, wherein q is a predefined natural number, 
 modifying the at least one layer dataset such that a temporal sequence for the scanning of the respective object cross-section with energetic radiation is specified such that at least one portion of the bottom surface region, or at least one portion of the top surface region, is scanned before all other positions to be solidified of the object cross-section; and 
 providing at least one layer dataset that has been modified by the layer dataset modification unit for the generation of a control dataset for the layer-wise additive manufacturing apparatus. 
 
     
     
       13. The method of  claim 12 , further comprising
 a computer-based method of providing control data for a layer-wise additive manufacturing apparatus for manufacturing an object, 
 wherein in the layer-wise additive manufacturing apparatus the object is manufactured by a layer-wise application of a building material onto a support or a previously applied layer of the building material and by a solidification of the building material by a supply of radiation to positions in a layer that correspond to the cross-section of the object in this layer in that the positions are scanned with energetic radiation by an energy input unit such that the energy input unit directs at least one energy beam to predetermined positions of a layer of the building material so that a solidification of the building material is effected by the energy beam, 
 wherein the method of providing control data comprises: 
 a first step of accessing a plurality of layer datasets comprising data models of a plurality of building material layers to be selectively solidified during the manufacture and lying immediately one over the other, wherein each layer dataset comprises a data model in which positions corresponding to an object cross-section are marked, wherein a solidification of the building material in the respective layer occurs at the positions, and wherein in at least one layer dataset a bottom surface region of an object cross-section exists in the corresponding data model, wherein the bottom surface region is defined such that in at least one of p layers below the bottom surface region no solidification of building material is specified, wherein p is a predefined natural number, and/or a top surface region of an object cross-section exists, wherein the top surface region is defined such that in at least one of q layers above the top surface region no solidification of building material is specified, wherein q is a predefined natural number, 
 a second step of modifying the at least one layer dataset such that a temporal sequence for the scanning of the respective object cross-section with energetic radiation is specified such that at least one portion of the bottom surface region, or at least one portion of the top surface region, is scanned before all other positions to be solidified of the object cross-section; and 
 a third step of providing the at least one layer dataset that has been modified in the second step for the generation of a control dataset for the layer-wise additive manufacturing apparatus. 
 
     
     
       14. A method for controlling a layer-wise additive manufacturing process for manufacturing an object, wherein the object is manufactured by a layer-wise application of a building material and by a solidification of the building material by a supply of radiation to positions in a respective horizontal layer that correspond to a respective cross-section of the object, comprising:
 providing an energy input unit that directs at least one energy beam to predetermined positions of the layer of the building material so that the solidification of the building material is effected by the energy beam; 
 providing a plurality of layer datasets comprising data models of layers of the building material to be selectively solidified during the manufacture and wherein the layers of the building material lie immediately one over the other, the object having certain layers which form an interior region area of solidified material in a finished object where the certain layers in the interior region area are stacked one upon, the object further having perimeter portions of a respective cross-section which are outboard from the interior region area and when solidified have unsolidified powder material above or below the perimeter portions, respective perimeter portions constituting less than a respective cross-section of a layer; and 
 solidifying a respective perimeter portion in a layer as a whole before solidifying of a remainder of the cross-section constituting the interior region area for a layer. 
 
     
     
       15. The method of  claim 14 , wherein the interior region area is a sandwich region of stacked layers in the finished object, the perimeter portions with unsolidified material below are downskin regions, and the perimeter portions with unsolidified material above are upskin regions. 
     
     
       16. The method of  claim 14 , wherein the unsolidified powder material is immediately above or below the perimeter portions.